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Clinical and Translational Medicine Jul 2022An impeccable female meiotic prophase is critical for producing a high-quality oocyte and, ultimately, a healthy newborn. SYCP3 is a key component of the synaptonemal...
BACKGROUND
An impeccable female meiotic prophase is critical for producing a high-quality oocyte and, ultimately, a healthy newborn. SYCP3 is a key component of the synaptonemal complex regulating meiotic homologous recombination. However, what regulates SYCP3 stability is unknown.
METHODS
Fertility assays, follicle counting, meiotic prophase stage (leptotene, zygotene, pachytene and diplotene) analysis and live imaging were employed to examine how FBXW24 knockout (KO) affect female fertility, follicle reserve, oocyte quality, meiotic prophase progression of female germ cells, and meiosis of oocytes. Western blot and immunostaining were used to examined the levels & signals (intensity, foci) of SYCP3 and multiple key DSB indicators & repair proteins (γH2AX, RPA2, p-CHK2, RAD51, MLH1, HORMAD1, TRIP13) after FBXW24 KO. Co-IP and immuno-EM were used to examined the interaction between FBXW24 and SYCP3; Mass spec was used to characterize the ubiquitination sites in SYCP3; In vivo & in vitro ubiquitination assays were utilized to determine the key sites in SYCP3 & FBXW24 for ubiquitination.
RESULTS
Fbxw24-knockout (KO) female mice were infertile due to massive oocyte death upon meiosis entry. Fbxw24-KO oocytes were defective due to elevated DNA double-strand breaks (DSBs) and inseparable homologous chromosomes. Fbxw24-KO germ cells showed increased SYCP3 levels, delayed prophase progression, increased DSBs, and decreased crossover foci. Next, we found that FBXW24 directly binds and ubiquitinates SYCP3 to regulate its stability. In addition, several key residues important for SYCP3 ubiquitination and FBXW24 ubiquitinating activity were characterized.
CONCLUSIONS
We proposed that FBXW24 regulates the timely degradation of SYCP3 to ensure normal crossover and DSB repair during pachytene. FBXW24-KO delayed SYCP3 degradation and DSB repair from pachytene until metaphase II (MII), ultimately causing failure in oocyte maturation, oocyte death, and infertility.
Topics: Animals; Cell Cycle Proteins; DNA-Binding Proteins; F-Box Proteins; Female; Meiosis; Mice; Prophase; Synaptonemal Complex; Ubiquitination
PubMed: 35858239
DOI: 10.1002/ctm2.891 -
Molecular Aspects of Medicine Jun 2024Meiosis is a critical step for spermatogenesis and oogenesis. Meiosis commences with pre-meiotic S phase that is subsequently followed by meiotic prophase. The meiotic... (Review)
Review
Meiosis is a critical step for spermatogenesis and oogenesis. Meiosis commences with pre-meiotic S phase that is subsequently followed by meiotic prophase. The meiotic prophase is characterized by the meiosis-specific chromosomal events such as chromosome recombination and homolog synapsis. Meiosis initiator (MEIOSIN) and stimulated by retinoic acid gene 8 (STRA8) initiate meiosis by activating the meiotic genes by installing the meiotic prophase program at pre-meiotic S phase. This review highlights the mechanisms of meiotic initiation and meiotic prophase progression from the point of the gene expression program and its relevance to infertility. Furthermore, upstream pathways that regulate meiotic initiation will be discussed in the context of spermatogenic development, indicating the sexual differences in the mode of meiotic entry.
Topics: Spermatogenesis; Humans; Meiosis; Animals; Male; Meiotic Prophase I; Prophase
PubMed: 38797021
DOI: 10.1016/j.mam.2024.101282 -
Annual Review of Genomics and Human... Aug 2023In meiosis, homologous chromosome synapsis is mediated by a supramolecular protein structure, the synaptonemal complex (SC), that assembles between homologous chromosome... (Review)
Review
In meiosis, homologous chromosome synapsis is mediated by a supramolecular protein structure, the synaptonemal complex (SC), that assembles between homologous chromosome axes. The mammalian SC comprises at least eight largely coiled-coil proteins that interact and self-assemble to generate a long, zipper-like structure that holds homologous chromosomes in close proximity and promotes the formation of genetic crossovers and accurate meiotic chromosome segregation. In recent years, numerous mutations in human SC genes have been associated with different types of male and female infertility. Here, we integrate structural information on the human SC with mouse and human genetics to describe the molecular mechanisms by which SC mutations can result in human infertility. We outline certain themes in which different SC proteins are susceptible to different types of disease mutation and how genetic variants with seemingly minor effects on SC proteins may act as dominant-negative mutations in which the heterozygous state is pathogenic.
Topics: Male; Female; Humans; Mice; Animals; Synaptonemal Complex; Chromosome Pairing; Meiosis; Infertility; Mutation; Mammals
PubMed: 37159901
DOI: 10.1146/annurev-genom-110122-090239 -
Nature Structural & Molecular Biology Apr 2023Cohesins are ancient and ubiquitous regulators of chromosome architecture and function, but their diverse roles and regulation remain poorly understood. During meiosis,...
Cohesins are ancient and ubiquitous regulators of chromosome architecture and function, but their diverse roles and regulation remain poorly understood. During meiosis, chromosomes are reorganized as linear arrays of chromatin loops around a cohesin axis. This unique organization underlies homolog pairing, synapsis, double-stranded break induction, and recombination. We report that axis assembly in Caenorhabditis elegans is promoted by DNA-damage response (DDR) kinases that are activated at meiotic entry, even in the absence of DNA breaks. Downregulation of the cohesin-destabilizing factor WAPL-1 by ATM-1 promotes axis association of cohesins containing the meiotic kleisins COH-3 and COH-4. ECO-1 and PDS-5 also contribute to stabilizing axis-associated meiotic cohesins. Further, our data suggest that cohesin-enriched domains that promote DNA repair in mammalian cells also depend on WAPL inhibition by ATM. Thus, DDR and Wapl seem to play conserved roles in cohesin regulation in meiotic prophase and proliferating cells.
Topics: Animals; Meiosis; Chromosomal Proteins, Non-Histone; Chromosomes; Cell Cycle Proteins; Chromosome Pairing; Caenorhabditis elegans; Mammals; Cohesins
PubMed: 36879153
DOI: 10.1038/s41594-023-00929-5 -
Genes & Genetic Systems Jun 2022Meiosis is a crucial process for spermatogenesis and oogenesis. Initiation of meiosis coincides with spermatocyte differentiation and is followed by meiotic prophase, a... (Review)
Review
Meiosis is a crucial process for spermatogenesis and oogenesis. Initiation of meiosis coincides with spermatocyte differentiation and is followed by meiotic prophase, a prolonged G2 phase that ensures the completion of numerous meiosis-specific chromosome events. During meiotic prophase, chromosomes are organized into axis-loop structures, which underlie meiosis-specific events such as meiotic recombination and homolog synapsis. In spermatocytes, meiotic prophase is accompanied by robust alterations of gene expression programs and chromatin status for subsequent sperm production. The mechanisms regulating meiotic initiation and subsequent meiotic prophase programs are enigmatic. Recently, we discovered MEIOSIN (Meiosis initiator), a DNA-binding protein that directs the switch from mitosis to meiosis. This review mainly focuses on how MEIOSIN is involved in meiotic initiation and the meiotic prophase program during spermatogenesis. Further, we discuss the downstream genes activated by MEIOSIN, which are crucial for meiotic prophase-specific events, from the viewpoint of chromosome dynamics and the gene expression program.
Topics: Chromosome Pairing; Humans; Male; Meiosis; Mitosis; Spermatocytes; Spermatogenesis
PubMed: 34955498
DOI: 10.1266/ggs.21-00054 -
Genes Apr 2022During meiosis, homologous chromosomes must recognize, pair, and recombine with one another to ensure the formation of inter-homologue crossover events, which, together... (Review)
Review
During meiosis, homologous chromosomes must recognize, pair, and recombine with one another to ensure the formation of inter-homologue crossover events, which, together with sister chromatid cohesion, promote correct chromosome orientation on the first meiotic spindle. Crossover formation requires the assembly of axial elements, proteinaceous structures that assemble along the length of each chromosome during early meiosis, as well as checkpoint mechanisms that control meiotic progression by monitoring pairing and recombination intermediates. A conserved family of proteins defined by the presence of a HORMA (HOp1, Rev7, MAd2) domain, referred to as HORMADs, associate with axial elements to control key events of meiotic prophase. The highly conserved HORMA domain comprises a flexible safety belt sequence, enabling it to adopt at least two of the following protein conformations: one closed, where the safety belt encircles a small peptide motif present within an interacting protein, causing its topological entrapment, and the other open, where the safety belt is reorganized and no interactor is trapped. Although functional studies in multiple organisms have revealed that HORMADs are crucial regulators of meiosis, the mechanisms by which HORMADs implement key meiotic events remain poorly understood. In this review, we summarize protein complexes formed by HORMADs, discuss their roles during meiosis in different organisms, draw comparisons to better characterize non-meiotic HORMADs (MAD2 and REV7), and highlight possible areas for future research.
Topics: Cell Cycle Proteins; Chromosome Segregation; Meiosis; Spindle Apparatus; Synaptonemal Complex
PubMed: 35627161
DOI: 10.3390/genes13050777 -
PLoS Genetics Nov 2023The centromere is an epigenetic mark that is a loading site for the kinetochore during meiosis and mitosis. This mark is characterized by the H3 variant CENP-A, known as...
The centromere is an epigenetic mark that is a loading site for the kinetochore during meiosis and mitosis. This mark is characterized by the H3 variant CENP-A, known as CID in Drosophila. In Drosophila, CENP-C is critical for maintaining CID at the centromeres and directly recruits outer kinetochore proteins after nuclear envelope break down. These two functions, however, happen at different times in the cell cycle. Furthermore, in Drosophila and many other metazoan oocytes, centromere maintenance and kinetochore assembly are separated by an extended prophase. We have investigated the dynamics of function of CENP-C during the extended meiotic prophase of Drosophila oocytes and found that maintaining high levels of CENP-C for metaphase I requires expression during prophase. In contrast, CID is relatively stable and does not need to be expressed during prophase to remain at high levels in metaphase I of meiosis. Expression of CID during prophase can even be deleterious, causing ectopic localization to non-centromeric chromatin, abnormal meiosis and sterility. CENP-C prophase loading is required for multiple meiotic functions. In early meiotic prophase, CENP-C loading is required for sister centromere cohesion and centromere clustering. In late meiotic prophase, CENP-C loading is required to recruit kinetochore proteins. CENP-C is one of the few proteins identified in which expression during prophase is required for meiotic chromosome segregation. An implication of these results is that the failure to maintain recruitment of CENP-C during the extended prophase in oocytes would result in chromosome segregation errors in oocytes.
Topics: Animals; Meiosis; Chromosome Segregation; Drosophila Proteins; Prophase; Centromere; Drosophila; Mitosis; Kinetochores; Centromere Protein A; Chromosomal Proteins, Non-Histone
PubMed: 38019881
DOI: 10.1371/journal.pgen.1011066 -
Journal of Molecular Cell Biology Sep 2022Meiosis is essential for evolution and genetic diversity in almost all sexual eukaryotic organisms. The mechanisms of meiotic recombination, such as synapsis, have been...
Meiosis is essential for evolution and genetic diversity in almost all sexual eukaryotic organisms. The mechanisms of meiotic recombination, such as synapsis, have been extensively investigated. However, it is still unclear whether signals from the cytoplasm or even from outside of the cell can regulate the meiosis process. Cilia are microtubule-based structures that protrude from the cell surface and function as signaling hubs to sense extracellular signals. Here, we reported an unexpected and critical role of cilia during meiotic recombination. During gametogenesis of zebrafish, cilia were specifically present in the prophase stages of both primary spermatocytes and primary oocytes. By developing a germ cell-specific CRISPR/Cas9 system, we demonstrated that germ cell-specific depletion of ciliary genes resulted in compromised double-strand break repair, reduced crossover formation, and increased germ cell apoptosis. Our study reveals a previously undiscovered role for cilia during meiosis and suggests that extracellular signals may regulate meiotic recombination via this particular organelle.
Topics: Animals; Male; Zebrafish; Cilia; Meiosis; Chromosome Pairing; DNA Repair
PubMed: 35981808
DOI: 10.1093/jmcb/mjac049 -
International Journal of Biological... 2022About 10% of reproductive-aged couples suffer from infertility. However, the genetic causes of human infertility cases are largely unknown. Meiosis produces haploid... (Review)
Review
About 10% of reproductive-aged couples suffer from infertility. However, the genetic causes of human infertility cases are largely unknown. Meiosis produces haploid gametes for fertilization and errors in meiosis are associated with human infertility in both males and females. Successful meiosis relies on the assembly of the synaptonemal complex (SC) between paired homologous chromosomes during the meiotic prophase. The SC is ultrastructurally and functionally conserved, promoting inter-homologous recombination and crossover formation, thus critical for accurate meiotic chromosome segregation. With whole-genome/exome sequencing and mouse models, a list of mutations in SC coding genes has been linked to human infertility. Here we summarize those findings. We also analyzed SC gene variants present in the general population and presented complex interaction networks associated with SC components. Whether a combination of genetic variations and environmental factors causes human infertility demands further investigations.
Topics: Adult; Animals; Chromosome Segregation; Female; Germ Cells; Humans; Infertility; Male; Meiosis; Mice; Synaptonemal Complex
PubMed: 35342360
DOI: 10.7150/ijbs.67843 -
Annual Review of Cell and Developmental... 2008Accurate segregation of chromosomes during meiosis requires physical links between homologs. These links are usually established through chromosome pairing, synapsis,... (Review)
Review
Accurate segregation of chromosomes during meiosis requires physical links between homologs. These links are usually established through chromosome pairing, synapsis, and recombination, which occur during meiotic prophase. How chromosomes pair with their homologous partners is one of the outstanding mysteries of meiosis. Surprisingly, experimental evidence indicates that different organisms have found more than one way to accomplish this feat. Whereas some species depend on recombination machinery to achieve homologous pairing, others are able to pair and synapse their homologs in the absence of recombination. To ensure specific pairing between homologous chromosomes, both recombination-dependent and recombination-independent mechanisms must strike the proper balance between forces that promote chromosome interactions and activities that temper the promiscuity of those interactions. The initiation of synapsis is likely to be a tightly regulated step in a process that must be mechanically coupled to homolog pairing.
Topics: Animals; Centromere; Chromosome Pairing; Chromosome Segregation; Chromosomes; Meiosis; Nuclear Envelope; Recombination, Genetic; Synaptonemal Complex
PubMed: 18597662
DOI: 10.1146/annurev.cellbio.23.090506.123245